Ignition system employing a fast high magnetic buildup



Dec. 20, 1966 H. WALD 3,293,492

IGNITION SYSTEM EMPLOYING A FAST HIGH MAGNETIC BUILDUP Filed July 8, 1963 2 Sheets-Sheet l F|e.| FIG.3

INVENTOR. v

BYWWM .H. WALD 3,

IGNITION SYSTEM EMPLOYING A FAST HIGH MAGNETIC BUILDUP Dec. 20, 1966 Filed July 8, 1963 2 Sheets-Sheet 2 F|e.7B

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U INVENTOR. BY M W I United States Patent 3,293,492 IGNITION SYSTEM EMPLOYING A FAST HIGH MAGNETIC BUILDUP Herman Wald, Astoria, N.Y. (97-11 Horace Harding Expressway, Queens, N.Y. 11368) Filed July 8, 1963, Ser. No. 293,480 8 Claims. (Cl. 315-180) This application is a continuation-impart of my copending application entitled, Electric Ignition Control Circuit for Internal Combustion Engines, Serial No. 50,623, filed Aug. 19, 1960.

This invention is related to improvements in ignition systems for multi-cylinder internal combustion and like engines.

With the trend towards higher compression ratios in the design of new engines, greater magnetic input energy with following higher secondary voltages are required to provide the necessary breakdown voltage of the spark-plug for an eflicient ignition performance throughout the speed range, since the breakdown strength of the gasoline mixture is proportionately increased.

Thus it is highly desirable that the sparking high-voltage pulse shall be maintained even when the plugs are fouled causing its equivalent shunt resistance to drop as low as 100,000 ohms.

It is generally known that such a system, consisting of an inductive circuit repeatedly closed and opened for a series of short time-intervals, naturally takes its maximum current under low-speed driving conditions and, therefore, the value of the current interrupted decreases as the speed increases.

The existence of the aforesaid condition is based on the law of growth of current in an inductive circuit. The intensity of the primary current at the moment of the break is mainly determined by the time-duration during which the contact points are closed, thus permitting the magnetic flux in the core to build up to a magnitude of saturation depending upon this closure time. Unless the building up of the flux about the core is taking place to a rather high degree of intensity, the breaking of the primary current by the separation of the contact points, will not result in sufficient action of the collapsing magnetic flux about the secondary winding to generate a secondary spark of enough intensity to jump the spark plug gap under all conditions of engine operation, such as very high speed, cold start, leaky plugs, etc.

Since the amount of input energy is proportional to the engine speed, the problem of the ignition unit is, therefore, simply that of providing the energy necessary to raise the secondary systemthe capacitance associated with plugs, cables, distributor and a portion of the distributed capacitance of the winding itselft0 the sparking breakdown potential of the plug-p0ints. Consequently, the general problem in any coil ignition system, therefore, resolves itself into obtaining a value of the interrupted current suificient to ensure efiicient ignition, but without an excessive current at low speeds. In other words, it is of great importance to produce an efficient and possibly constant energy output throughout the speed range and variable operating conditions.

At the present art systems the performance at slow speed driving is always low because of the limitations in the current handling ability of the breaker contact surfaces without becoming oxidized, therefore the high currents which occur at low speeds may easily lead to complete ignition failure. Although an increase of the inductance of the primary coil would actually decrease the current intensity level and improve to certain extent the performance at low speeds, however, it may seriously affect the 3,293,492? Patented Dec. 20, 1966 energy output at high speeds with reduced closing timeperiod.

The attainment of this goal is, however, greatly limited by the present design conditions making extremely diflicult the proper proportioning of the coil-inductance for providing the maximum possible storage energy at any particular engine speed or closing time-period. In practice, the present design method adopted a compromise solution in selecting a coil-inductance to produce an appreciably reduced energy storage taken as an average throughout the speed range.

The primary object of the present invention consists of controlling the rate of increase of current through the primary coil inductance to thereby provide an improved ignition system for multi-cylinder internal combustion and like engines which materially increases the effective spark-energy output in accordance with the requirements of any given speed range and without increasing its normal cam speed used in the present art.

The present invention, therefore, contemplates the provision of means associated with the primary inductance providing above automatic control of the time-constant of the circuit parameters to thereby permit an extreme rapid building up of the magnetic flux in the core to a higher output than hitherto in spite of the available insufiicient time duration during which the contact points are closed under given speed of operation.

One of the broader objects of the present invention aims at providing a so-called compound transient effect to be obtained by a sudden change of the parameter or timeconstant of the primary circuit within the available closing time-period. Thus, a new transient process is produced while the current is yet in a period of transient from a previous starting shock, causing a more rapid increase or time-differential of the primary current so as to allow a relatively high initial current at the start of the next transition period. Consequently the desired magnitude of current at break could be obtained at the end of the said second transition period at comparatively high speeds, which in turn maybe transformed into higher secondary voltage-output.

Another important object of the invention is the provision of continuously variable speed responsive compensating device associated with the primary inductance to effect a variation of the parameter or time-constant of the primary circuit at the first transient stage so as to become proportional to the changes in speed and thereby to compensate for any variation in the magnitude of current at break being attributable to said changes in speed. The proportionality in magnitude of the compensating device is predetermined so as to secure a substantially constant intensity of current break throughout any speed range of operation and at the same time to prevent the passage of current through the primary circuit in excess of the permissibile limit value at low speeds. This is mainly effected in such a manner that at any speed the desired magnitude of current increase to the end of the second transition period is just reached at the moment of break.

It is an added object of the present invention to provide various type of improved speed responsive compensating devices such as the existing governor or accelerator pedal of the conventional type or other conventional means for controlling the above constancy in reaching the desired current intensity at the moment of break to suit any particular application.

A further object of the invention is to apply an increased primary inductance to produce an increased spark energy during starting or other abnormal operating conditions, but without increasing the normal magnitude of current at break to be attained by controlling the duration of the first transition period during which the auxiliary breaker contacts insert in series with the battery source one selected portion of the primary winding.

It is a final object of the invention to secure all the higher energies accumulated in the inductance at the moment of break to be transferred into the secondary equivalent capacitance providing a desired maximum amplitude of voltage pulse. This is obtained by the application of an auxiliary series spark-gap in the secondary circuit having a breakdown potential to correspond to the desired voltage peak.

Further objects of the invention lie in the combination of the various above mentioned arrangements to form various complete electric ignition control devices and also include the various combinations and subcombinations of elements and their inter-relation.

The objects of the invention will evident from the detailed description taken in conjunction with the accompanying drawings and for fuller understanding reference will be made to them, in which:

' FIGURE 1 illustrates the circuit diagram of the ignition control representing the basic principle of the invention to produce a compound-transient effect for decreasing the rise time of current in an inductive circuit of the coil-ignition system including an automatic speed responsive compensating means.

FIGURE 2 illustrates a time-curve of the transient current produced at the closing of the ignition coil circuit.

FIGURE 3 represents the time-variation of the compound-transient current curves produced by a sudden change in the circuit para-meters while the current is yet in a period of transition from a previous transient condition, and indicating the different limiting cases providing different methods of operation.

FIGURE 3A represents the current-rise curves in the primary ignition coil circuit under various speeds in applying the automatic speed responsive compensating device in accordance with the invention.

FIGURE 4 show-s the time-variation of the transient current components through the interrupter during the separation of the auxiliary breaker contacts providing a complete sparkless interruption.

FIGURE 5 is a diagrammatic representation of a conventional coil ignition system-circuit showing all the circuit parameters including the secondary distributed capacitances.

FIGURE 5A represents an equivalent diagram of the coil ignition circuit.

FIGURE 5B illustrates a train of secondary voltage oscillations produced upon break of the primary circuit, including the increased maximum amplitude of secondary voltage pulse.

FIGURE 6 is a diagrammatic illustration of a modified embodiment using a series auxiliary spark-gap and increase of primary inductance.

FIGURES 6A and 6B show the operating curves of the embodiment of FIGURE 6.

FIGURE 7 represents a series of curves showing the dependence of coil performance with varying speed of the engine and with increasing inductance.

FIGURE 7A represents the present limitations imposed upon coil design such as, heating, arcing, etc., and the curves express the voltage required for various steadystate currents under different closing time-periods or engine speed.

FIGURE 7B illustrates the variation of the sparkenergy with engine speed.

FIGURE 7C shows the intensity of the primary current at break under various speeds.

FIGURE 7D represents the power variation in the circuit.

FIGURE 7E shows the variation of the resistive and inductive powers during both transition periods.

FIGURE 8 is a diagram of a speed responsive device with various operating methods adapted to insert in series with the battery source any portion of the primary winding.

FIGURE 9 shows a preferred diagrammatic arrangement of the complete ignition control circuit as applied to a conventional distributor system operating with a variable tapping on the primary winding.

While many preferred embodiments of the invention will be described herein, it is contemplated that considerable variation may be made in the method of procedure, arrangements, or use for other applications without departing from the spirit of the invention. In the following description parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

BASIC PRINCIPLE OF OPERATION (1) Compound transient condition Referring first to FIGURE 1, there is illustrated a basic ignition control circuit consisting of an ignition coil transformer generally indicated at 1, having a primary winding L and secondary winding L The primary winding L includes the series combination of the parameters R L and R L in series with a constant voltage source or battery E, and a switch S to close only the parameter R L into the battery circuit and switch S to close the complete circuit, where R and R are the ohmic resistances of the self inductances L L respectively, therefore are not shown separately. Also it is assumed that lumped RL parameter includes the sum of the above both series parameters R L and R L The switch S is shunted by the conventional condenser C and switch 5 may close into the battery circuit any tapped portion of the parameter R L to be automatically controlled in response of the variation of engine speed or repetition rate of the contact switching. However, the condenser through its charge being momentary considered as an interruption in the R L parallel branch and tapping adjustments are now disregarded at the following discussion. It is noted that by varying the tapping connection, the magnitude of the R L parameter is changed in such a manner that its relative proportion with respect to R L is varied correspondingly. The compensating speed responsive means generally'denoted by reference numeral 2 actuates the setting of the tapped connection on the primary winding L in response of repetition rate of the switching of the contact S In order to determine the nature of the transient current variation that follows the sudden application of a constant potential difference E to such a circuit, let at the time moment t=0 the switch S to be closed at first to insert into the battery circuit the parameter R L while S is open with the parameter R L as being effected by a suitable sequentially timed breaker contact pair operating in accordance with the invention. The corresponding time-variation of the transient current is represented by the curve i of FIGURE 3, which also illustrates all other transient conditions.

The condition for dynamic equilibrium is given by the expression di, R Z +L d tE (1) and the complete transient solution for the current i; may be expressed explicitly as a function of time;

where t is the length of time the contacts are closed as expressed in seconds, and e is the Napierian logarithm base 2.718.

Thus the time constant t may be represented in FIG- URE 2 as the crossing point of lines E/L and E/R denoted by the letter 0. However, We see that the current for the case with resistance present starts out along this straight line E/L and soon bends away from it and runs off asymptotic to the final va-lue E/R.

It is known that the inductance property of the circuit is associated with energy storage in the magnetic field. In other words, the stored energy cannot be changed instantaneously, hence it the circuit parameter or applied voltage is suddenly changed, the current in the circuit has the same value immediately after the change as it had immediately before the change. This important phenomenon is known as the continuity condition for the current in an inductive circuit.

It is important to note that the current in the circuit adjusts itself from any given initial value i(0) to the permanent value on an exponential curve which, however, may even completely disappear if the initial value i(0) happens to coincide or nearly equal with the final steady-state current demanded by the parameters of the circuit existing at the moment the change of the parameters occurs in this new transient state.

In accordance with the present invention, its main principle is based upon the previously outlined continuity of transient phenomena, in providing a compound-transient current flow to be effected by a sudden change in the circuit parameters while the current is yet in a period of transition from a previous transient condition. This sudden change consists of inserting the parameter R L into an ER L circuit before the current has reached or just reaching its steady-state value demanded by the voltage and final series parameters of the circuit.

The transition of current during the first period lasting from the time of closing switch S to the time of opening switch S has been defined in the Equation 2. Let S, be opened, S closed at 1 it is noted that in practice a slight overlapping may occur as S must be already closed when S opens. This time moment becomes a new startingpoint in the further analysis, and therefore the above equation is used as a new boundary condition. The expression for the current after t is given by:

E 1+ n), 6 (L1+ 2) where t is reckoned anew, that is, to be equal to zero at the time of opening switch S The value of the constant of integration 0 is found by substituting the i at 1 from Equation 2, thus By imposing the new boundary condition upon the above Equation 4, we may obtain the final expressed on:

R 6 R +R s From the current curve i representing the current flow in the circuit of FIGURE 1, it may readily be seen that at the switching time-moment r it reaches a new initial value A indicated by the ordinate in FIGURE 3, which is somewhat less than the steady-state value that would be established after insertion of the new parameter R L in the above circuit. The current curve i shown with continued dashed lines represents the time-variation of the actual current flow for the case if the circuit parameter R L would remain unchanged and without disturbance until it reaches its final steady-state value. The corresponding time-constant t is determined by the crossing point of the slope line E/L with the steady-state line E/R It is quite evident that by properly selecting the value of the parameter R L and the predetermined switching time-difierence (t t of the cooperating contact switches S and S of FIGURE 1, an extremely rapid rise or rate of change of current could be accomplished during the first transition period (r -r thereby producing a magnitude of current that may possibly reach an approximate value of the desired final steady-state demanded by the circuit. Thus, immediately after the new second transition period starts, a full saturation of a given inductance coil may be attained within both transition periods consisting of a limited short time-interval. As outlined previously, this is due to the continuity condition whereby the new initial current of relatively high magnitude quickly adjusts itself to the desired permanent value and providing an exceedingly rapid energy-storage into the newly inserted inductance parameter R L upon the start of the second transition period. The time-duration (I -r shown on FIGURE 3, required for reaching the steady-state magnitude of the current shown by curve 2A is, under given parameter R L mainly determined by the proper selection of the time-moment i when the switching action of S takes place. As a consequence, the compound-transient process actually provides a considerable reduction of the resulting-time-constant of the equivalent circuit of FIGURE 1 including both parameters R L and R L in series.

(b) Limiting case occurs when the value of the expression (6) of the former case becomes exactly equal to E/R -I-R Under such favorable operating condition the value of i in Equation 5 expressing the transition of current at the second period will be reduced tothe steadystate value E/R +R of the total circuit.

In this case the transient component may completely disappear at the second switching action of S However, it has mainly a theoretical importance since it is almost impossible to manage such an exact timing for starting the second transition period.

(c) Overlimited case represented by the curve 3 of FIGURE 3, occurs when the value of the expression (6) is greater than E/R +R The time variation of this curve during the first transition period shows that the switching action of S took place at such a time-moment t when the current has already been increased above the actually required steady-state value. From the characteristic of the current curve 3 We may see that it reaches the permanent value on an exponentially decaying curve up to the time-moment t The resulting time-duration including both transition states required to reach the desired steady-state value is the longest one among the three mentioned cases. It follows that the delay of the second switching action of the switch S at 1 may proportionately increase the time required for obtaining the aforesaid permanent steady-state value of the current.

Under abnormal operating conditions this case, however, may bring definite advantages if a higher current flow than the normal steady-state value would be required. In such case the final interruption of the circuit by switch S may be effected before the current declines to the normal steady-state value, whereby the accumulated energy at the break is increased in proportion to the higher current. Accordingly, higher-secondary voltages could be supplied to the spark-plugs as hitherto has been attainable irrespective of the engine speed, as it will be explained in a more detailed manner in connection with FIGURE 6B.

Curve 4 of FIGURE 3 represents the current rise under normal conditions when both parameters R L and R L are initially in the series circuit and t denotes the time required for reaching its steady-state value. Thus by virtue of the compound-transient effect according to the principles of this invention, the resulting gain in time is given by the diiference of I and any of the t time-moments depending upon the selected operating conditions regarding the transition periods. The result thus obtained may be very significant in order to satisfy certain operating speeds and optimum performance.

(la) Separation process of contacts S .Gener-ally speaking, at any interrupting process when the flow of current through the external circuit reduces to zero, the high inductance and short duration At of interruption will develop a rupturing voltage which is much higher than the system voltage. This is due to the rapid change of current at the end in the external circuit causing a high inductive interrupting voltage, as being determined by the full contact resistance and inductance of external circuit.

The main characteristic feature of opening the switch S however, lies in the fact that a substantially same magnitude of current flow is maintained during and after full separation, provided S is already fully closed when S switch opens, and thus no interrupting voltage can occur and the possibility of any arcing at the contracts are completely eliminated.

The time variation of the transient current components through the interrupter and R L branch parameter are represented on FIGURE 4 by the curves i and i respectively. As we see that the curve i exhibits an exponentially declining current due to the change of the interface resistance whereas the curve i shows a corresponding rising current into the parameter branch R L Thus, we may derive the important conclusion that by virtue of the continuity law the steady-state current of the external battery circuit will continuously flow during the separation time At of the switch S and is merely decomposed into the two components i and i which are oppositely equal in magnitude, and given by:

from 1:0, to t=At, during the complete separation time period of the contacts.

Hence the external battery circuit is free from any transients by maintaining the continuous flow of the physically impossible as it would require an infinite rate of change of stored energy, however, an extremely rapid storage is possible due to the force of the continuity law, the duration of which may follow the falling characteristic curve i or rising curve i shown on FIG. 4.

(1b) Automatic speed responsive device.-An additional novel feature of the invention comprised in FIG- URE 1 is the provision of an automatic speed responsive compensating device denoted by reference numeral 2, being adapted to set into circuit any arbitrary portion of the primary Winding in dependence upon the prevailing speed of the engine to control the current rise accordingly. By the provision of continuously variable speed responsive device, to be described in detail in the application part, the constancy of stored energy under various speeds may finally be obtained by virtue of its association with the primary inductance. This may effect a variation of the time-constant of the primary circuit at the first transition state by connecting a proportionate portion of the primary coil inductance in such a manner as to always obtain the approximate full steady-state current I just after a very short time the portion L is reinserted in series with L in order to get the full current I at break and also the full energy in the total inductance L +L independent of any variation of the speed or closing time-period. This will further provide a high efficiency at low speeds as at this speed the full magnitude of current is just reached at the break and not earlier.

FIGURE 3A illustrates the variation of the current rise corresponding to the requirements of the various speeds or time-closure periods in the primary coil circuit. Curve 5 represents the current rise under the previously described high speed limit, whereas curve 8 illustrates the current rise at the lowest speed. The other curves 6, 7, respectively, correspond to the intermediate speed range.

At high speed limit, the portion L of the primary coil inductance to he open circuited is the largest one in order to get the more rapid increase of the current to the end of the first transition period t reaching the magnitude of current nearly the steady-state value I to be completed at 1 through a slight rise of i At the intermediate speeds, however, a proportionately smaller portion of L is open-circuited to produce a relatively lower current rise during the first transition period so as to provide during the second transition period from Z to t a current rise of nearly approaching the desired steady-state value I, as required to match the particular speed, as shown on curve 6, and likewise the time periods t respectively, correspond to the speed conditions shown on curve 7. Finally, at the lowest speed limit curve 8, only a very mini-mum portion of L is open circuited during the first transition period up to the time-moment t so that practically a great portion of the coil operates to slow down the rate of current rise of i Hence the additional magnitude i of current rise during the second transition period up to L time-moment during which the entire coil is operating, that is (L +L may complete it to an approximate magnitude of the desired steady-state value I All the above current curves exhibit .a main characteristic feature of the invention which consists of automatically controlling the magnitude of the relative portions L L of the coil inductance operating at the respective transition periods. Thereby we are able to control the time-constant during both consecutive periods to suit for any particular speed or closing time-period. Consequently, the resulting time-constant of the complete closing time-period will definitely provide a total current-rise during said both transition periods just approaching the steady-state value I of the current at the moment of breaking the circuit. This may be expressed by:

being valid for any speed, where the magnitudes of both component currents are already derived in Equations 4 and 5, respectively, in paragraph (1).

The great importance of this feature lies in the fact that a constant energy at the break is practically produced throughout the desired speed range and at the same time the unnecessary losses, due to the conversion into heat by the effect of the circuit resistance, are greatly reduced, at low-speeds. The great improvement in efficiency at low speeds is mainly achieved by the fact that the current rise to the required maximum is delayed by proportionately selecting the duration of both consecutive transition periods in conjunction with the selection of the open-circuited portions of the primary inductance L, until the end of the second transition period when the break of the circuit takes place, therefore unnecessary losses are eliminated, such as heating the primary coil during a large portion of the closing time and drawing full current from the battery increasing its consumption.

The operation of the above described speed responsive device is based on the application of various tappings on the primary inductance coil in order to vary the portion of the self-inductance to be open-circuited during the first transition period in accordance with the varying speed of the engine.

FIGURE 5 is basically a diagrammatic representation of an identical coil ignition circuit. In such a system the high voltage secondary winding L is connected to the spark plug by means of a distributor and the low voltage primary winding L is in series with the battery E and cam operated interrupter switch S which is shunted by the conventional condenser C for enabling the current to keep flowing a short time-interval after interruption. At the moment of break the circuit being shock excited to provide a damped sine voltage-wave oscillation of high amplitude necessary for the spark-discharge in the secondary circuit.

The ignition coil is generally considered to be a closecoupled system with damping and shunted across the secondary winding L by the equivalent capacitance C being equal to (C +C )/r where r is the ratio of secondary to primary turns. It is noted that C is the capacitance associated with plugs, cables, distributor and some portion of the distributed capacitance of the winding itself. The system is also shunted by the resistance R representing the iron losses in the core and R is the total equivalent shunting resistance made up of R and any possible external load. This condition is clearly shown on the equivalent circuit diagram of FIG. 5A, where L is the inductance of the secondary winding with the primary open circuited.

In view of representing the decay of current and growth of voltage in a damped inductive circuit, it may readily be shown by standard methods of circuit analysis that the differential equation representing the instantaneous voltage V across the secondary terminals of FIGURE 5A, follow ing the momentary interruption of the primary circuit or current flow is defined by:

'i V 1 dV V dt 13, (it LC From the above Equation 10 we obtain for the first voltage peak V =V D, which may be transformed into a more convenient expression by equating the electromagnetic and electrostatic energies as follows:

/2V,,C= /21 L yielding for V =I /(L /C), consequently we obtain:

V h/(D L /c) (11) where I is the primary current and the radical expression (14) may be defined as the current-factor of the coil and it may express the secondary voltage produced in units of KV per ampere of primary current broken. By disregarding the variability of D and C, this current-factor is mainly proportional to the square root of the primary L consequently the secondary voltage is so directly proportional to the input energy having great importance in the operation of the principle of the invention. It shall be noted that by increasing the self-inductance of the primary-but without the normally following decrease of the primary currentas provided in this invention, much higher energies or voltage peak may be produced in proportion to the longer oscillating resistance.

As we outlined previously, by action of the parallel capacitance, after interruption the produced voltage-surge overshooting the battery voltage is does not jump suddenly to its maximum value but rather reading its peak only after one-quarter of the natural period determined by L and C. Curve 12 of FIGURE 5B illustrates this oscillating condtion and also indicates the time within which the breaker contact S must have separated widely enough to avoid any are formation. Therefore, the assurance of the required contact switching-velocity is better accomplished with a comparatively larger condenser, however, a relatively smaller condenser would provide a considerably higher voltage swing. Thus the final solution must always be a compromise between rapid switching action and correspondingly small condenser in order to satisfy both requirements for an efficient operation.

The total equivalent shunt resistance was determined by the prevailing damping of the secondary circuit. In practice at the most coil designs the total equivalent R ranging between 0.25 to 2 megohms, except the plugs in fouled condition when it decreases to as low as 100,000 ohms, but as an average value we assume 0.5 megohm.

In order to examine the possibility of increasing the current-factor or secondary voltage-amplitude by maintaining the maximum current intensity and increasing the inductance alone, we bring a brief view of the present design conditions with optimum coil inductance. It is known that an increase of the winding ratio rather decreases the current-factor because of the damping and other factors entering into the picture. It is clear from the current factor expression that with coils having the same damping and C, the current factor becomes proportional to the primary inductance and consequently the secondary voltage would, in turn, be directly proportional to the input energy. However, this is not the case even though the same winding-ratio is maintained, since if L is varied the damping factor D including the term L /D will change as L is varied; whereas if the secondary inductance L is kept constant by changing L with the primary turns, C will vary and with it D also. It follows that if for a given coil of given primary inductance the winding ratio is increased, the damping must also increase with increase of the secondary inductance.

The increase of the self-inductance by increasing the n number of turns will rather be permissible in accordance with the invention, whereby the limitations in selecting the optimum inductance are substantially released. As a result, the optimum may be selected to be a considerably increased inductance without adding iron to the circuit which may increase the damping.

(3) Control discharge with auxiliary spark-gap in secondary circuit As described in the foregoing chapter and defined by Equation 11, the first secondary voltage peak V is always proportional to the available total damping of the secondary circuit including that of the main spark-plug gap.

Thus it is highly desirable that the sparking high-voltage pulse shall be maintained even when the plugs are fouled to some degree causing its shunt resistance to the secondary circuit to drop as low as 100,000 ohms resulting from a low horsepower use for an appreciable time.

Therefore it is necessary that a very rapid build-up of high voltage across the secondary shall cause a breakdown before there is a heavyenergy loss in the shunt resistance of the plug. This is of primary importance where it is desirable to produce a peak-voltage of about 30 kv. having a rise time of a few microseconds and at the same time limiting the magnitude of current through the breaker points to about 34 amperes.

FIGURE 6 represents another modified embodiment of the invention employing a sealed type auxiliary series spark-gap in the secondary circuit. The main object of the modified arrangement is, therefore, to secure that all energy stored in the magnetic field shall substantially be transferred to the equivalent total capacitance including distributed capacitances of the secondary circuit or system for the time-moment when the actual discharge may invariably take place in order to produce a voltage-pulse of maximum amplitude. Thus it will provide a full utilization of the higher energies being accumulated at the break irrespective of the engine speed or repetition rate of the breaker points.

To accomplish the above objective, a series auxiliary spark-gap generally indicated at SG arranged within a gas filled chamber or any other conventional sealed type gap being provided in series with the main spark-gap MSG of the secondary circuit. This series spark-gap SG is so constructed that the peak amplitude of the high frequency voltage oscillation at the quarter of the cycle, as deter mined by the resonant circuit, shall attain a predetermined magnitude shown with the curve 13 on FIGURE 58, and shall correspond to the break-down tension of both series gaps including the main spark-gap. However, the breakdown is largely determined by the setting of the auxiliary series gap potential.

As a result, the discharge time-moment is being controlled by the said auxiliary series spark-gap in a manner such that when the maximum amplitude of the oscillatory charging is reached, by virtue of the break-down of the seriesgap, an extremely rapid and almost aperiodical conversion of the full available energy will take place within the main spark-plug gap.

The energy applied to the main spark-plugs is thus also controlled by the breakdown voltage and limits the available maximum high frequency voltage amplitude, despite of the available higher energies in accordance with the invention, as shown by curve 12 on FIGURE 58. Hence the combined series break-down voltage will be of the order of approximately the maximum available amplitude of voltage oscillation of the novel system arrangement of the invention which is considerably higher than hitherto has been attained with the present art. Since both gaps the auxiliary series gap as Well as the main spark plug gap are in series, neither gap will breakdown prior the maximum voltage pulse-amplitude is reached whereupon the full discharge of the plugs will follow.

Accordingly, the great importance of the usage of the series auxiliary spark-gap SG lies in the fact that the resulting equivalent-damping is considerably reduced in allowing a maximum voltage pulse-amplitude to appear as being produced by the available higher stored energies in accordance with the invention.

It shall further be noted that the auxiliary series sparkgap is specifically well adapted to this type of application since the break-down of the auxiliary gap is always secured by the constant mmimum amplitude of the voltagepulse provided in this invention irrespective of the engine speed or repetition rate of the breaker contacts. When considering the variable pulse-amplitudes of the present art, the application of such a series spark-gap in series with the secondary circuit will cause an unsafe operation because the variable voltage-pulse amplitude may oftentimes not reach the predetermined or set break-down tension of the series spark-gap causing an ignition failure.

As a comparative illustration, the curve 14 represents the amplitude of the voltage-pulse with the conventional design of the present art using cam operated breaker points.

(4) Constancy of stored energy under various speeds The amount of energy stored in the magnetic field of the coil inductance is dependent upon the magnitude of the current flowing therethrough at the time the breaker contacts open, thereupon this available energy is released quickly and precipitated suddenly into the secondary winding causing a rapid rise of voltage to initiate a spark at the plug electrodes. Consequently the efiiciency of the spark-discharge is dependent upon said available energy which, however, varies with the speed of operation or time of closing the breaker contacts.

In this view, the present art adopted a compromise solution at the selection of the optimum coil-inductance to obtain an acceptable performance under various speeds.

operation.

In the present ignition coils, the self-inductance L may be defined in terms of the energy stored for a given current, as expressed by:

In order to obtain the optimum conditions we have to differentiate Equation 12 with respect to L and equate'to zero.

As an approximate solution of (12), the optimum conditions may be obtained finally by the form:

Rt/L=1.256 (13) With this result given in (13), we are enabled to proportion the coil-inductance for providing the maximum possible storage energy at any particular engine speed or closing time. Thus the series-curves plotted on FIGURE 7 hav been derived from diiferent values of. Rt or speed to illustrate the dependence of coil performance with increasing primary inductance (in mH. values). The curve .21 indicates the variation of the current-factor (as defined in Formula 11) vs'. increasing inductance, whereas on the curves 15, 16, 17 allowance has been made for various speeds that the current has not reached its steadyst-ate value. the current at break is actually expressed as a fraction of the steady-state value which decreases correspondingly as the inductance increases.

It is important to note that all these curves 15, 16, 17 indicate a maximum value of the secondary voltage obtained corresponding to a definite primary inductance. In other terms, they show that for any given time of closure there exists a corresponding optimum value of the primary inductance which, for that particular time of close, will always provide the maximum performance.

In view of the above mentioned compromise solution, in actual practice the coil is designed so as to correspond to the intersection of the curve 21 with thercurves 15, 16, 17, respectively, at the points 18, 19, 20, respectively, and depending on the selected speed limit of the particular coil to be designed. With this'design method the coil will perform satisfactorily, and equally good Within the required speed range, although with appreciably reduced energy storage taken as an average throughout the speed range. The variation of the spark-energy in the present practical design of the coil within a speed range of 500- 4000 r.-p.m., is represented by the curve 24 of FIGURE 73. At low speeds the spark-energy i sabout 0.03 joule per spark and falls away rapidly towards 2000 rpm. and more slowly thereafter, reaching a value of about 0.007 joule at 4,000 r.p.m.

FIGURE 7A represents the presently imposed limitations on coil design. These limitations are such as heating under steady-state current, arcing at the contacts, and the discussed limitations in selecting the optimum coil-inductance. These curves here shown are actually derived from that of FIGURE 7, and may express the voltage re quired for various steady-state currents under difierent closing time-periods.

As will be seen on the derived curves, that form certain milliseconds of closure neither 6 nor 12 volt input would be suitable since by using a low inductance with 6 volt the arcing limit is exceeded, whereas with 12 volt the heating limit is exceeded. However, there are also curves for certain time of closure (milliseconds) the 6 volt as well as the 12 volt is just suitable for an efiicient It is Worth mentioning a type of curve seen with relatively large inductance and large closing time when using 12 volt, it will definitely result in exceeding the heating limit. It is clear that the differences in operating conditions are caused by the fact that the same inductance-coil is used for different speeds or time 'of closure.

Hence, at higher speeds for any closing-time 13 the application of 12 volt input would need too high inductance to be economical.

The rising primary current curve 25 of FIGURE 7C may serve as a further practical illustration of the conditions at the present art. If the selected particular coil design gives the optimum performance at the high speed limit of 4,000 r.p.m., the current at break is obtained by substituting the value in (13), and we get:

We assume a 6 cylinder engine having a spark frequency of 200 per second and at 0.66 closing time we get only a closed period of 0.0033 sec. By taking a steady-state current of 3.2 amp, the value of the current at break would :be 3.2 0.7l4=2.4 amp, and the average current is 0.8 amp, resulting in an energy consuming by the coil of about watts.

Whilst at low speeds the performance of the same coil will be relatively very low as hereinafter explained. At 500 r.p.m. the closed period is 0.025 sec., and if we assume a steady-state current of 3.2 ampere to be reached in about 0.015 sec., the average current flowing in the circuit is about 2 amp, and therefore the energy consumed by the coil amounts to 12 watts, which is excessively high current consumption.

At any rate the stored energy under optimum closingtime conditions t of any given engine speed may be found to have its maximum value W by substituting the expression Rt /L=l.256,

Furthermore, the energy consumed by the battery in establishing the magnetic field is equal to:

f "E1dzE1f 1 yn 0 0 e (16) after integrating and substituting the expression (14), yields to:

energy drawn from battery. Finally the ratio of energy stored to energy consumed would be:

or 47% efficiency under optimum operating conditions.

In accordance with the novel method of the present invention a compound-transient process is basically produced, whereby the full energy storage into the ignition coil takes place during two consecutive transition-periods.

The energy delivered to theR L circuit during the first transition period may be subdivided into two parts. One portion of the energy R 11 is transformed into heat as a result of passage of current through R whereas the remainder energy L 1 is stored in the magnetic field that links the turns L Due to the fact that the current at the early part of the transient period increases at the rate of E/L units per second along an approximate straight line with E/L slope, it follows that the whole applied voltage is substantially used in the inductance L and the resistive drop is quite negligible since the current curve i 'bends away only at some higher values as shown on FIGURE 3. This condition is likewise represented on FIGURE 7D, and it is clear that the inductive power curve 27 at the moment t shown at 29 represents almost the whole resulting power of curve 28, as the resistive power curve 26 did not rise yet appreciably at this moment when the rate of change of current might already change to (ER i )/L Thus by virtue of the negligible power loss in the resistive part, a very efiicient storage into the magnetic field of the inductance L may be obtained during the first transition period. Thereafter it follows the opening of the switch S of FIGURE 1, for inserting in series the remaining portion R L of the coil.

Referring now again to FIGURE 4, there has been shown that during the separation time At of the interi4 rupter switch S the initial value of the current i due to the continuity law, may continue to flow by being decomposed into two components.

The energy input into the magnetic field of L during At is t i ii W =J; LZZ-idt= Lidt=%L I (19) The important feature of this expression (19) is that the energy input into the branch L is completely independent of the time-variation of the current as it changes from 0 t0 Since the total magnetic field required in the coil inductance (R L +R L is almost established at the end of At, therefore, a further increase of the magnetic energy during the following very short time interval (t ,,t that elapses until the condenser becomes inserted in series by the breaker contact S on FIGURE 5, is negligibly small as shown on curve i of FIGURE 3. This is due to the fact that as soon as the current nearly approaches the steady-state current demanded by the total series circuit, there is practically no further energy storage into the magnetic field of the complete final circuit, therefore the energy input during the second transition period may be expressed by:

Some energy, however, is converted into heat by the effect of the total series resistances R and R respectively.

In summarizing, the magnetic input energies during both consecutive transition periods may be obtained as follows:

so the total magnetic input energy is:

FIGURE 7E clearly shows the variation of the resistive and inductive components of the total power as well as the total power. During the first transition period the inductive power curve 33 shows a rapid rise up to the time-moment i as explained in connection with FIG- URE 7D, and jumps during At switching period (when L becomes inserted in series), to a magnitude of nearly equal to the desired maximum storage indicated at 34, while at the end of the second transition period t it drops almost suddenly to zero because the total required magnetic field has already been established and the current-flow becomes quasi constant, thereby any further energy input has practically been ceased.

The resistive power curve 35 shows only a very slight increase up to the time-moment 1 thereafter rises rapidly up to the end t of the second transition period indicated at 36. The actual appreciable resistive loss may start from this time-moment when all further energy input to the circuit would be converted to heat, however, this loss is stopped to continue by sudden breaking the circuit as required to provide the desired shock-oscillation. The total power variation is represented by the curve 37.

The efficiency of operation at the high speed limit in accordance with the invention may be found as follows:

In employing the same coil being used in the conventional design under optimum conditions having the value Rr /L=1.256 established by Formula 11, the current of break was 0.7411 in Equation 14, and W was 0.2El z (Equation 15). Due to the fact that in this case the full steady-state value of the current I is reached, it is quite clear that the maximum energy stored would be:

' rnary inductance.

as compared to 43% of the conventional case under an operation with optimum selected coil.

It is important to note that the above difference in efficiency is accomplished with using the same optimum self-inductance as being selected to match the presently limited design conditions with an operating efliciency depending on the variable speeds as shown on FIGURE 7 (different Rt curves).

() Compound transient surge for increased spark-energy A further increase of energy or secondary voltages could be produced by the application of the overlimited case (c) in using two difierent methods:

(A) Increase of primary inductance-The increase of self-inductance may actually cause a decrease of the primary current to be broken, however, the lengthening of the first transiton period, by changing the duration of the auxiliary switching action may provide a higher initial current rise, whereby it may maintain at the moment of break the previous magnitude of steady-state current.

As it may be seen on the typical operating curves shown on FIGURE 6A, the new magnitude of the steady-state current required by the increased self-inductance has been reduced to a value I represented by the curve 39. In order to produce a current at break having the same magnitude I as the steady-state value before the insertion of the auxiliary inductance or increase of the original inductance, we produce, 'by a corresponding setting of the duration of the auxiliary switching action during the first transition period, an initial current rise up to point F such that the decaying curve 38 will just reach the desired original steady-state value I at the end of the second transition period T The above operating condition is made possible by the application of the overlimited case (c) where according to the expression (6) the magnitude of current at break may be greater than required by the parameters of the circuit, that is E/R +R With this method of operation we are ableto provide an increase of the spark-energy at break, but without increasing the magnitude of current above the permissible limit, as being solely due to increased inductance.

Thus the constancy of the current intensity at break is maintained despite of increased inductance, consequently the dashed line curve 22 of FIGURE 7 expresses the relation of the secondary voltage with increasing inductance in accordance with Equation ll in which the current-factor is proportional to the square root of the pri- Thus the dependence of the current intensity on the coil-resistance-inductance or time during which the circuit is closed, is completely released and therefore any desired increase of the secondary voltage may be accomplished, although with certain limitations on the winding ratio of the primary to secondary.

The above method may also be applied for compensating the loss of energy due to drop of the battery-voltage under starting or other unusual operating conditions. In order to obtain the desired compensation for the reduced energy, an arrangement similar to that described in FIG- URE 6A will be employed to provide the required control of the duration of the first transition period resulting in a higher initial current rise and thereby to maintain the magnitude of current at break despite the drop in battery-voltage. In this case the control action will be only a temporary function.

Another important feature of the invention may be derived from the above operating method of increasing the primary inductance. This method may be applied to good advantage under normal running conditions in order to reduce the magnitude of the primary current at break to a desired lower level and still maintaining the same energy output. Such a reduction of current-intensity at break being handled by the contact surfaces of the breaker points will definitely provide a longer contact life and safer operation.

It shall be noted that due to the release of the timeconstant limitations including the selection of the optimum primary inductance, the same energy output may be obtained by increasing the inductance if at the same time the first transition period is changed correspondingly so that after the initial current rise the following decaying current curve shall reach the reduced current at break I at the end of the second transition period similarly as shown on FIGURE 6A. With this method the decrease of current at break is compensated by the corresponding increase of inductance for producing the same energy output.

FIGURE 6 illustrates a modified and improved embodiment of the invention to work in conjunction with the operating'curves represented on FIGURE 6A for obtaining an increased energy output by increasing the primary inductance as a temporary function or under normal running conditions.

Accordingly the new elements to be introduced in this figure are the auxiliary coil having a winding L 2. manually operable starting switch S Normally the starting switch S short circuits the auxiliary winding L and it will be opened whenever an increase of the inductance is desired.

The adjustment is made by selecting the initial tapping point on the primary such as to obtain the necessary change in the relative duration of the first transition pe riod T to reduce the current to I at the end of the second transition period T shown on FIGURE 6A. In order to obtain a constant energy output, we reduce the decaying current at the end of the second transition period T to the reduced current value I The loss of energy due to drop of the battery-voltage under starting or unusual operating conditions may be compensated by controlling the duration of the relative first transition period, which will result in a correspondingly higher initial rise of current such that the decaying current at the end of the second transition period.

An increase of the primary current-under constant inductance-above the steady-state value required by the circuit parameters, may be produced according to the current surge-curve 43 of FIGURE 6B, by properly changing the ratio of the first to second transition periods or the portions of the R 11 and R L to 'be controlled. Thereupon the current may somewhat decay exponentially to the end of the second transition period at T time moment, shown on curve 44 which, if not interrupted, it would approach asymptotically on an exponentially decaying line to the final steady-state value of the current, as shown with the dashed line curve 45, and the current surge 43 will provide an extremely rapid charge into the total primary inductance L -l-L as explained in connection with FIGURE 3 of the overlimited case (c). The curve 46a shows the rise to the normal steady-state value of current.

Accordingly the final amplitude of the current surge at break is indicated by the ordinate 46 reaching a magnitude I and the instantaneous energy may be expressed by the formula:

Thus the final energy obtained is considerably higher. This method, however, is limited by the maximum permissible intensity of current to be broken by the contacts without to provide any damaging action of the contact surfaces.

The application of the above methods are specifically advantageous under starting or other unusual operating conditions.

FIGURE 9 shows a preferred arrangement of the complete ignition control circuit in a diagrammatic form as applied to a conventional distributor system used in internal combustion engines and supplemented by an auxiliary breaker-arm arrangement to operate with the control method using a variable tapping on the primary winding as shown by the slidable control arm 102 and lever means 100 leading to the speed responsive device generally denoted by the numeral 2. The variable tapping method is treated in a detailed manner in FIGURE 8.

This FIGURE 9 includes a battery 51, one side of which is grounded through conductor 65 leading to one end of the primary winding 50A, while the other terminal of the battery is connected to the conventional ignition switch 55 through conductor 66. The general reference character 67 designates a conventional distributor being provided with an additional auxiliary breaker arm 68, the movable contact 69 of which is connected to the movable contact 77 of the main breaker arm 76 while its fixed contact 78 is connected through conductor 70 to the other terminal of the primary winding 50A. The ignition switch 55 is connected to the common point of the movable contacts 69 and 77 and the relatively fixed contact 71 is connected through conductor 72 to slidable control arm 102, contact surfaces 103 and variable tapping 73 of the primary 50A to form a closed battery circuit at the first closing of the contact pair 69, 71 of the auxiliary breaker arm 68. It further includes a rotatable shaft 74 provided with a cam 75. A bridging condenser 56 is connected across the contact points 77, 78 of the main breaker 76 being otherwise mounted in a manner well known in the art.

As outlined in FIGURE 1, both cooperating contact pairs operate in a sequential order so that at first the auxiliary contacts 69, 71 close and then contacts 77, 78 close just before opening of the contacts 69, 71.

One side of the secondary winding 50B is commonly connected to the primary winding through conductor 80 and its other terminal connected to the conventional distributor by means of conductor 81. The distributor is provided with a plurality of terminals each of which connected to a spark plug in the usual manner, however, for the sake of simplicity only one spark plug 82 is shown.

For the sake of simplicity in the diagrammatic representation shown on the FIGURE 9 each of the movable auxiliary breaker-arms 68 and 76 is disposed on a breakerarm bracket 83 with an elongated hole 84 to effect the desired maximum adjustment for locating same in a proper relation to the other fixed breaker-arm 76 as being required for an eflicient operation in accordance with the invention. Furthermore, a cam denoted by the numeral 75 with two oppositely located lobes 85, 86, out of a plurality of lobes, are shown in an approximate proper operating condition.

For proper switching of both cooperating contactpairs, the cam with its lobes must be designed and adjusted in such a manner that both movable contacts 69 and 77 shall close in a sequential order, whereas the movable contact 69 shall open at the time-moment when the current in the portion 64 of the primary coil 50A is closed into the battery circuit and has attained nearly the desired maximum or steady-state value which may be accomplished by a predetermined revolution of the cam 75.

It should further be noted that both breaker-arms 68 and 76 are arranged in a circumferentially spaced relationship around the common rotatable cam 75 for periodically actuating their respective contacts by means of rubbing blocks 87, 88, respectively, in the usual manner. The main breaker-arm 76, being spring influenced, carries the movable contact 77 coacting with the stationary 18 contact 78 so as to normally maintain a closed position at the recessed portion 79 of the cam 75, all well known in the present art. It is finally noted that various commercially available double breaker-arm units can be adopted to operate in conjunction with the principles of the invention. Also single breaker-arm arrangements with cooperating double contact pairs can be used to advantage, provided there is adjustment made for proper switching time displacement in the desired sequence. The usage of single breaker-arm method would greatly simplify the practical application of the invention. The detailed description of such arrangement is deemed unnecessary as it is well known to those skilled in the art.

FIGURE 8 represents a modified embodiment of the invention showing a diagrammatic view of a speed responsive compensating device in combination of a control arm and switching means being adapted to insert into the battery circuit any predetermined portion of the primary winding depending upon the prevailing speed or time of closure of the primary circuit. Reference numeral 2, as in FIG. 1, designates such an assembly designed to automatically control the magnitude of the relative portions of the primary winding inductance to be inserted into the battery circuit, thereby to provide a constant current magnitude at break under various speeds, as previously explained and shown on current curves of FIG. 3A.

It shall be noted that in this speed compensating method the conventional double breaker-arm with twocontact-pair arrangement, not shown here, can preferably be used when adjusted to provide an operation in the properly timed sequence. The requirements of such sequential operation is that at first the auxiliary breaker contacts close to insert a portion 64 of the primary winding into the battery circuit allowing a rapid current rise during the first transition period and then the main breaker contacts close just before the auxiliary contacts open.

The speed compensating device 2 may preferably consist of any of the following devices:

(a) A centrifugal governor otherwise used to advance the timing of the spark-discharge which may at the same time also perform this work. Generally in all such constructions there is a system of weights which are forced to move under the influence of centrifugal force and this controlled movement produces an angular displacement between the driving and driven shafts which, in turn, increases with the speed. Thus the weights of the governor tend to fly apart, whereby they draw a sleeve along the shaft making a partial revolution which may be transferred to a lever means to actuate a corresponding displacement of a switching means generally indicated at 101 being adapted to insert in series with the battery circuit any portion of the primary winding 50A in proportion with the displacement of the lever means, the movement of which is dependent upon the speed of the engine.

(b) Another speed responsive device would be the throttle linkage denoted by the general numeral 2A actuated by depressing the accelerator pedal which is then interlocked with the control arm 102 to provide the desired control in response of the throttle opening being dependent on the speed. The extent of the arm movement in relation to the throttle opening is made adjustable to conform the control requirement with varying speed.

(c) Another alternate embodiment of the speed responsive device would be a diaphragm denoted by the numeral 2B actuated by the vacuum pressure in the engine manifold which, in turn, may be linked to the control arm 102 to provide the same control efiect in accordance with the engine speed controlling the vacuum pressure.

It is assumed that the primary winding is spaced outside for a faster heat dissipation, so this fact makes easier to carry out the required tapping on the primary coil to provide a plurality of individual inductors 50C, D, E, F, G. The switching means 101 includes also a plurality of the contact surfaces denoted by the numeral 103 in circumferential arrangement which are insulated from each other and rigidly secured. Each contact surface 103 of the switching means 101 is electrically connected to one tap of the winding 50A. The rotatable control arm 102 is slidably disposed and interlocked with the lever means 100, thereby to provide the desired control 'efiect by means of the mentioned speed responsive devices 2A, 2B, 2C. 1

' Of course, the more tappings are provided, the better or smoother is the control of the stepwise arrangement applied to any of the mentioned speed responsive devices.

'While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the spirit of the invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An auxiliary ignition control device for use in ignition systems of internal combustion and like engines comprising an ignition transformer coil for accumulating magnetic energy including a primary winding having a plurality of tapped portions, a source of voltage supply, a circuit breaking means, an electrical main circuit including said primary winding, said voltage source and said circuit breaking means in series for recurrently closing and opening said main circuit to control the rate of input current pulses eifecting a recurrent storage of energy from said source, the duration of said input pulses includes a first and second transition periods, including in combination, an auxiliary switching device connected in parallel with any of said tapped portions of said primary winding with inclusion of said voltage source forming an auxiliary circuit, said auxiliary switching device selectively inserting any of said tapped portions into said auxiliary circuit and open same immediately after said circuit breaking means closes and having a speed responsive device adapted to control the tapping connection to any of said tapped portions of said primary winding becoming eifective in said auxiliary circuit in response to mechanical means controlled by the speed of said engine, said auxiliary switching device opens any of said portions of said primary winding just prior the current reaches its normal steady-state value demanded by said whole primary winding allowing to reach in said main circuit at the end of said second transition period a substantially constant steady-state current irrespective of the rapidity of said input pulses.

2. An auxiliary ignition control device as defined in claim 1 wherein said auxiliary switchingdevice opens any of said portions of said primary Winding at instants of time when the current has reached a value considerably higher than the steady-state current demanded by the whole primary winding during said first transition period, thereby to produce an increased magnetic energy storage -into said primary winding during said second transition period.

3. An auxiliary ignition control device for use in ignition systems of internal combustion and like engines comprising an ignition transformer coil for accumulating magnetic energy including a primary winding having a plurality of tapped portions, a source of voltage supply, a

circuit breaker means, an electrical main circuit including said primary Winding, said voltage source and said circuit breaker means in series for recurrently closing and opening said main circuit to control the rate of input current pulses effecting a recurrent storage of energy from said source, the duration of said input pulses includes a first and second transition periods, including in combination, an auxiliary switching device connectedin parallel with any of said tapped portions of said primary winding with trolled by the speed of said engine.

4. An auxiliary ignition control device for use in ignition systems of internal combustion and like engines comprising an ignition transformer coil for accumulating mag netic energy including a primary Winding having a plurality of tapped portions, a source of voltage supply, a circuit breaking means, an electrical main circuit including said primary winding, said voltage source and said circuit breaking means in series for recurrently closing and opening said main circuit to control the rate of input current pulses effecting a recurrent storage of energy from said source, the duration of said input pulses includes a first and second transition periods, including in combination, an auxiliary switching device connected in parallel with any of said tapped portions of said primary winding with inclusion of said voltage source forming an auxiliary circuit, said auxiliary switching device selectively inserting any of said tapped portions into said auxiliary circuit and open same immediately after said circuit breaking means closes and having a speed responsive device controlling the tapping connection to any of said tapped portions of said primary winding, said speed responsive device comprises a movable lever means in combination with a slidable switching means comprising a plurality of contact blades in a circumferential arrangement, each of said tapped portions of said primary winding being connected to the respective contact blades, said speed responsive device being interlocked with said lever means to actuate a proportionate displacement of said slidable switching means independence of the varying engine speed to engage successively each of said contact blades, said slidable switching means selectively inserting in said auxiliary circuit any tapped portion of said primary'winding corresponding to said displacement in order to provide a corresponding magnitude of initial current rise during said first transition period securing a substantially constant steady-state current at break.

tributor system includes a rotatable cam with lobes cooperating with said breaker arms, both said breaker arms operatively engaging said cam during its rotation in such a sequential relationship that at first the contacts of said auxiliary switching device close and open immediately after said circuit breaker contacts close.

6. An auxiliary ignition control device as defined in claim 5 further comprises a condenser connected .across said circuit breaker contacts, a secondary winding, a spark plug connected across said secondary winding, the periodical opening and closing of said circuit breaker contacts shock excite said condenser in said main circuit producing a series of sparks at said spark plug, the control action of said speed responsive device in response of the repetition rate of said input current pulses provides a substantially constant magnitude of secondary voltage at said spark plug irrespective of the rapidity of said input current pulses.

7. An auxiliary ignition control device as defined in claim 5 further comprises an auxiliary spark gap means in series with the secondary circuit of said ignition transformer coil, said auxiliary spark gap means being interposed in series circuit relationship with said ignition spark plug, the breakdown potential of said auxiliary spark gap means being set to a predetermined high peak magnitude of voltage being substantially equal to the maximum attainable magnitude of voltage pulse, the breakdown potential of said ignition spark plug is below that of said auxiliary spark gap means, said auxiliary spark gap means being adapted to operatively connect said secondary circuit with said ignition spark plug when the amplitude of the secondary voltage oscillation at the end of a quarter cycle reaches its maximum predetermined peak value, thereby to prevent the damping effect of the secondary circuit including said spark plug.

8. An auxiliary ignition control device as defined in claim 5 further comprises; an auxiliary inductor inter- References Cited by the Examiner UNITED STATES PATENTS 873,954 12/1907 Michel 315222 X 1,019,354 3/1912 Podlesak 315-222 X 1,374,205 4/1921 Hunt 315222 X 2,090,365 8/1937 Harris 315-222 X JAMES W. LAWRENCE, Primary Examiner. GEORGE N. WESTBY, DAVID J. GALVIN, Examiners. C. R. CAMPBELL, Assistant Examiner. 

1. AN AUXILIARY IGNITION CONTROL DEVICE FOR USE IN IGNITION SYSTEMS OF INTERNAL COMBUSTION AND LIKE ENGINES COMPRISING AN IGNITION TRANSFORMS COIL FOR ACCUMULATING MAGNETIC ENERGY INCLUDING A PRIMARY WINDING HAVING A PLURALITY OF TAPPED PORTIONS, A SOURCE OF VOLTAGE SUPPLY, A CIRCUIT BREAKING MEANS, AN ELECTRICAL MAIN CIRCUIT INCLUDING SAID PRIMARY WINDING, SAID VOLTAGE SOURCE AND SAID CIRCUIT BREAKING MEANS IN SERIES FOR RECURRENTLY CLOSING AND OPENING SAID MAIN CIRCUIT TO CONTROL THE RATE OF INPUT CURRENT PULSES EFFECTING A RECURRENT STORAGE OF ENERGY FROM SAID SOURCE, THE DURATION OF SAID INPUT PULSES INCLUDES A FIRST AND SECOND TRANSITION PERIODS, INCLUDING IN COMBINATION, AN AUXILIARY SWITCHING DEVICE CONNECTED IN PARALLEL WITH ANY OF SAID TAPPED PORTIONS OF SAID PRIMARY WINDING WITH INCLUSION OF SAID VOLTAGE SOURCE FORMING AN AUXILIARY CIRCUIT, SAID AUXILIARY SWITCHING DEVICE SELECTIVELY INSERTING ANY OF SAID TAPPED PORTIONS INTO SAID CIRCUIT BREAKING AND OPEN SAME IMMEDIATELY AFTER SAID CIRCUIT BREAKING MEANS CLOSES AND HAVING A SPEED RESPONSIVE DEVICE ADAPTED TO CONTROL THE TAPPING CONNECTION TO ANY OF SAID TAPPED PORTIONS OF SAID PRIMARY WINDING BECOMING EFFECTIVE IN SAID AUXILIARY CIRCUIT IN RESPONSE TO MECHANICAL MEANS CONTROLLED BY THE SPEED OF SAID ENGINE, SAID AUXILIARY SWITCHING DEVICE OPENS ANY OF SAID PORTIONS OF SAID PRIMARY WINDING JUST PRIOR THE CURRENT REACHES ITS NORMAL STEADY-STATE VALUE DEMANDED BY SAID WHOLE PRIMARY WINDING ALLOWING TO REACH IN SAID MAIN CIRCUIT AT THE END OF SAID SECOND TRANSISTION PERIOD A SUBSTANTIALLY CONSTANT STEADY-STATE CURRENT IRRESPECTIVE OF THE RAPIDITY OF SAID INPUT PULSES. 